This invention relates generally to golf balls, and more specifically, to a multi-layer golf ball and a composition therefore. In particular, this invention relates to a golf ball having a core, a cover and at least one intermediate layer disposed between the core and cover, wherein the cover or intermediate layer is formed from a blend comprising polyether-type thermoplastic polyurethane. The multi-layer golf balls of the present invention have been found to provide good distance, durability, and desirable playing characteristics.
Conventional golf balls can be divided into two general types or groups: solid balls or wound balls. The difference in play characteristics resulting from these different types of constructions can be quite significant.
Balls having a solid construction are generally most popular with the average recreational golfer because they provide a very durable ball while also providing maximum distance. Solid balls are made with a solid core, usually formed of a crosslinked rubber, which is encased by a cover material. Typically the solid core is formed of polybutadiene which is chemically crosslinked with zinc diacrylate and/or similar crosslinking agents and is covered by a tough, cut-proof blended cover. The cover is generally formed of a material such as SURLYN, which is a trademark for an ionomer resin produced by DuPont of Wilmington, Del. The combination of the core and cover materials provide a ball that is virtually indestructible by golfers. Further, such a combination imparts a high initial velocity to the ball which results in improved distance. Because the materials of which the ball is formed are very rigid, solid balls generally have a hard xe2x80x9cfeelxe2x80x9d when struck with a club. Likewise, due to their hardness, these balls have a relatively low spin rate which provides greater distance.
At the present time, the wound ball remains the preferred ball of more advanced players due to its spin and feel characteristics. Wound balls typically have either a solid rubber or liquid center core around which many yards of a stretched elastic thread or yarn are wound. The wound core is then covered with a durable cover material such as a SURLYN or similar material or a softer cover such as balata or polyurethane. Wound balls are generally softer and provide more spin than non-wound balls, which enables a skilled golfer to have more control over the ball""s flight and final position. Particularly, with approach shots into the green, the high spin rate of soft, wound balls enables the golfer to stop the ball very near its landing position.
A number of patents have been issued that are directed towards modifying the properties of a conventional solid ball by altering the typical single layer core and single cover layer construction to provide a multi-layer ball having such as a dual cover layer, dual core layer and/or a ball having a mantle layer disposed between the cover and the core. The inventions disclosed in the prior art patents are directed towards improving a variety of golf balls physical properties that help determine xe2x80x9cin-playxe2x80x9d characteristics.
Several patents are directed towards improving the carry distance of such balls. For example, U.S. Pat. No. 4,863,167 relates to a three piece solid golf ball having increased flight distance, wherein the ball has a center portion and an outer layer formed from a rubber composition, wherein the outer layer is harder than the center portion and further contains a gravity-adjusting filler so as to impart a higher specific gravity to the outer layer than that of the center portion. U.S. Pat. No. 5,184,828 relates to a solid three-piece golf ball having improved rebound characteristics and carry distance while maintaining an adequate spin rate, wherein these characteristics are allegedly obtained by controlling the size of the polybutadiene inner core and outer layer as well as their specific gravity and hardness. According to the ""828 patent, the key to obtaining the desired rebound characteristics is that the maximum hardness (42-62 Shore D) must be located at the interface between the core and the mantle and the hardness must then decrease both inwardly and outwardly. U.S. Pat. No. 4,714,253 is also directed towards a three-piece golf ball having an improved rebound coefficient. This golf ball has a core with a Shore C hardness of 57-80 in its center, but not more than 83 at a distance between 5-10 mm from its center and an outer layer with a Shore C hardness of 70-83.
Additionally, there are a number of patents directed towards improving the spin and feel of solid balls while maintaining the distance provided by the solid construction. For example, U.S. Pat. No. 5,072,944 discloses a three-piece solid golf ball having a center layer and an outer layer that are prepared from a rubber composition, wherein it is desirable that the center core layer is softer than the outer layer, the layers having a hardness (Shore C) of 25-50 and 70-90, respectively.
U.S. Pat. No. 4,625,964 relates to a solid golf ball having a polybutadiene rubber core of a diameter not more than 32 mm, a polybutadiene rubber intermediate layer having a specific gravity of lower than that of the core material, and a cover. U.S. Pat. No. 4,650,193 is directed towards a solid golf ball having a core comprising a central portion and an integral outer layer, wherein the core is a curable elastomer such as polybutadiene which is treated with a cure altering agent to soften an outer layer of the core, to produce a central layer with a hardness (Shore C) of greater than 75 and an outer layer with a hardness (Shore A) of less than 80.
U.S. Pat. No. 4,848,770 discloses a solid three-piece golf ball which includes a core of a highly filled synthetic rubber or polymeric material, an intermediate mantle of an unfilled synthetic rubber and a cover. The core and intermediate mantle have a hardness of between 50-95 Shore D. U.S. Pat. No. 5,002,281 is directed towards a three-piece solid golf ball which has an inner core having a hardness of 25-70 (Shore C), an outer shell having a hardness of 80-95 (Shore C) and a cover. Further, the specific gravity of the inner core must be greater than 1.0, but less than or equal to that of the outer shell, which must be less than 1.3.
The prior art discloses a variety of materials other than polybutadiene for use as intermediate layers. For example, U.S. Pat. No. 5,253,871 concerns a golf ball having a three-piece structure comprising an elastomer core, an intermediate layer of a thermoplastic material containing at least 10% of etheramide block copolymer, preferably blended with an ionomer, and a thermoplastic cover. U.S. Pat. No. 5,681,898 is directed to a multilayer golf ball having a conventional polybutadiene core, an ionomer cover and an intermediate layer formed from a blend of an ethylene methacrylic acid copolymer and a vulcanizate formed from polybutadiene and a peroxide curing agent.
U.S. Pat. Nos. 5,439,227 and 5,556,098 both disclose multilayer golf balls which have a conventional polybutadiene core, conventional covers and an intermediate layer formed from a polyetherester block copolymer blended with an ionomer.
Further, there are also several patents which are directed to golf balls having multiple cover layers. For example U.S. Pat. No. 4,431,193 relates to a golf ball having a multilayer cover wherein the inner layer is a hard, high flexural modulus ionomer resin and the outer layer is a soft, low flexural modulus ionomer resin, and wherein either or both layers may comprise a foamed ionomer resin. U.S. Pat. No. 5,314,187 also relates to golf balls having a multiple layer cover, wherein the outer layer is molded over the inner layer and comprises a blend of balata and an elastomer and the inner layer is an ionomer resin. U.S. Pat. No. 4,919,434 is directed towards a golf ball having a cover which comprises an inner layer and an outer layer, each of which comprise a thermoplastic resin. Preferably the layers are comprised of materials that are capable of bonding with each other, for example, by heat, or by other means which are readily known to one of ordinary skill in the art.
U.S. Pat. No. 5,813,923 discloses a golf ball having a core and a cover with an intermediate layer having a flexural modulus of less than 10,000 psi. The core has a compression of less than 70 and the cover has a flexural modulus of greater than 75,000 psi.
However, none of the patents discussed above disclose the multi-layer ball of the current invention that employs the materials, and has the improved golf ball properties, as disclosed herein.
The present invention is directed towards an improved multi-layer golf ball which includes a core having a compression of no greater than about 90, a cover having at least one layer being formed from a blend including a polyether-type thermoplastic polyurethane having a percent rebound resilience of greater than 60 such that the golf ball has a coefficient of restitution of greater than about 0.76.
In one embodiment, the blend further includes a second component, wherein the second component is a thermoplastic material. In another embodiment, the second component is selected from the group consisting of polyetherester block copolymers, polyesterester block copolymers, polyetheramide block copolymers, dynamically vulcanized thermoplastic elastomers, styrene-butadiene elastomers, other thermoplastic polyurethanes, thermoplastic polyesters, polymers formed using a metallocene catalyst, and blends thereof. Preferably, the second component is a polyetherester block copolymer. In another embodiment, the blend further includes a density adjusting filler in an amount sufficient to provide the at least one layer with a specific gravity of greater than about 1.2. In still another embodiment, the layer has a specific gravity of greater than about 1.25. Preferably, the density adjusting filler includes zinc oxide.
In another embodiment, the golf ball is comprised of a core, a cover and intermediate layer disposed there between. The intermediate layer is comprised of a blend of a polyether-type polyurethane having a percent rebound resilience of greater than 60 percent and another thermoplastic material. In a preferred embodiment, the blend includes about 20 to about 90 percent by weight polyether-type thermoplastic polyurethane, about 5 to 50 percent by weight second thermoplastic component and about 5 to about 40 percent by weight density adjusting filler. Preferably, the blend includes about 30 to 60 percent by weight polyether-type thermoplastic polyurethane having a percent rebound resilience of greater than 60, about 20 to 40 percent by weight second thermoplastic component and about 15 to 30 percent by weight density adjusting filler.
In another embodiment, the golf ball is comprised of a core, a cover and intermediate layer disposed there between. The intermediate layer has a Shore D hardness of about 25 to 50 and a flexural modulus of about 1,000 psi to 8,000 psi and is formed from greater than 50% pph of a polyether-type thermoplastic polyurethane. In another embodiment, the golf ball has a compression of no greater than about 90. In still another embodiment, the cover includes at least one of a thermoplastic or a thermoset material.
The present invention is also directed to a golf ball having a core including polybutadiene, a cover layer having a Shore D hardness of about 54 to 72, and at least one intermediate layer disposed between the cover and the core, wherein the at least one intermediate layer is formed from a blend including about 40 to 60 weight percent of a polyether-type thermoplastic polyurethane having a percent rebound resilience of greater than 60, about 15 to 30 weight percent of a density increasing or decreasing filler such as zinc oxide or barium sulfate or foaming agents or microspheres, from about 20 to about 40 weight percent polyetherester or polyesterester block copolymer; and wherein the golf ball has a coefficient of restitution of greater than about 0.78.
In one embodiment, the intermediate layer is formed from a blend including about 45 to 50 weight percent polyether-type thermoplastic polyurethane, about 18 to 22 weight percent zinc oxide, and about 30 to 35 weight percent polyetherester or polyesterester block copolymer. In another embodiment, the intermediate layer has a Shore D hardness of less than about 40 and a flexural modulus of less than about 10,000 psi.
The present invention is also directed to a golf ball having a coefficient of restitution of greater than about 0.78 and a compression of at least about 50 and less than 90, wherein the ball includes a core and a cover having at least an inner or an outer layer disposed concentrically about the core, wherein the layer is a composition including a polyether-type polyurethane derived from a diisocyanate reacted with a hydroxyl terminated polyether and a glycol chain extender composition. Preferably, the polyether-type polyurethane is blended with a thermoplastic selected from the group of homo and copolyesters, homo and co-polyamides, polyetherester block copolymers, polyesterester block copolymers, polyetheramide block copolymers, polyesteramide block copolymers, and other polyurethanes. The hydroxyl terminated polyether has alkylene oxide repeat units containing from 2 to 6 carbon atoms and a weight average molecular weight of at least 1,400. For a cover inner layer, the resultant material preferably has a flexural modulus less than 20,000 psi.
The present invention is also directed to a golf ball have a core comprised of a thermoset polybutadiene-rubber based material and a cover having an inner layer and an outer layer. The inner layer is particularly comprised of an injection moldable polyurethane having a percent rebound resilience of greater than 65 and a flexural modulus of less than 10,000 psi such that the ball has soft feel due to the low flexural modulus, a good initial velocity due to the high coefficient of restitution and is easy to manufacture since the inner layer is injection moldable. Even more preferably, the cover inner layer is injection molded at a temperature of less than 400xc2x0 F. Most preferably, the ball is manufactured by compression molding the core, injection molding the cover inner layer at a temperature of less than 400xc2x0 F. and compression or injection molding the cover outer layer from a thermoplastic material.
In another embodiment, the inner layer has a first hardness and the outer layer has a second hardness greater than the first hardness. When the cover hardness is greater than the inner layer and has a flexural modulus of greater than 60,000 psi, the ball will exhibit low spin off of the driver for excellent distance. In still another embodiment, the core has a third hardness within 10 Shore D of the cover inner layer hardness and less than the cover outer layer hardness. The softer core and cover inner layer contribute to the balls soft feel as well as low driver spin. In another embodiment, the inner layer has a specific gravity greater than about 1.2 for an increased moment of inertia.